This study is to identify patterns of zidovudine susceptibility among mother/infant pairs. Differences of mean zidovudine susceptibility between mothers who transmit and those who don't transmit HIV will be evaluated. All women will be receiving zidovudine. There is no additional drug given per protocol. Although this protocol has been open for some time, there have been no women enrolled. This protocol consulted with the GCRC Systems Manager for setup of the ACTG reporting software.